One dimensioning principle of elevator systems installed in buildings is their ability to serve elevator passengers in various traffic situations within a framework of desired service targets. Generally the transport capacity of an elevator system is dimensioned according to peak hours and not, e.g. according to average traffic needs, which means inter alia that the number of elevators of the elevator system must be selected to be so high that the elevator system can manage to meet the service targets set also during peak hours. The peak hours are often short-lived and in some cases even forecastable on the basis of the statistical information collected about the travel events of the elevator system. For instance, in office buildings it is typical that people working in the building arrive at their workplace at roughly the same time in the morning and cause so-called upward congestion in the elevator system and, correspondingly, when they leave the workplaces in the afternoon they cause so-called downward congestion in the elevator system. During other times outside peak hours an elevator system generally has unused transport capacity owing to the quieter traffic, in which case elevators stand unoccupied or they are underutilized most of the time.
Owing to the peak hours the elevator system must thus be “overdimensioned”, which causes considerable additional costs because, among other things, the speeds and number of elevators and/or the hoistway space required by elevators must be increased in order to achieve the desired transport capacity.
The number of stops made by elevators on the routes between the floors considerably affects the transport capacity of an elevator system and at the same time the number of elevators required. One prior-art method for improving the transport capacity and for reducing the number of stops is to use a destination control system for the control of the elevator system, in which control system each passenger indicates already at the departure floor the destination floor, to which he/she is traveling. Another prior-art method for improving the transport capacity and for reducing the number of stops is to divide the floors into zones such that each zone is served only by certain elevators of the elevator system. Elevator systems according to prior art, however, adapt badly to the traffic flows during peak hours, as a result of which the waiting times of passengers and/or other service times can increase to become unreasonable, if the elevator system is not sufficiently “overdimensioned” with respect to average traffic needs. There is thus a need for elevator systems that can better adapt to traffic flows during peak hours so that the need for overdimensioning of elevator systems would diminish and the elevator systems installed in buildings could be implemented more simply and with fewer elevators.